One thing to watch with a differentiator like that is that the input protection circuit of a CMOS IC, such as the 4017, is not overloaded when the pulse voltage goes beyond either supply rail.

 

I think we've established that he doesn't need a differentiator.

 

There is LT, now Analog Devices Timer Blox IC's https://www.digikey.com/en/product-highlight/l/linear-tech/timerblox? and a PC programmable 555 like timer.

 

After delving into the ICM7242 Timer datasheet I realize the following:






No problem getting the 10min, 20min, 40min, but I will need 2 additional IC's @ $270/ea. for which I have only one. Either that or I would need to switch between 3 separate RC networks. The timing part of the circuit would look like this:


I also believe I'd need to invert the signals from the ICM7242 to match the 4017.

 

If you need to invert a clock signal to a 4017, just tie the clock high and clock the CE instead.

 

I'm now eyeing the 4521 vs 4060 as I do not have 3 ICM7242's and they are $2.70/ea. I have both the 4521 and the 4060. I'm kinda leaning towards the 4521 Freq. Divider. Anyone know what value for Rs?




Oddly I see two different configurations for the chip regarding the Rs, Rtc & C.
There are two different datasheets for two different mfgr (MC14521 & CD4521).
The pinout is identical.

 

....but not a uC! I am dead-in-the-water with respect to uC's.
The entire project will be a Sequential Float Charger circuit using a single Float charger. I am looking to control the rotation of a half dozen Lead-Acid Batteries. My plan is to use a timer that will produce a charge time of 10, 20, or 40 minutes before switching to the next battery. My current dilemma is getting a somewhat stable time period out of the 555 timer. The circuit below is the general idea.

View attachment 168236
Not only am I looking for the ON times of 10min, 20minm 40min, but I am looking for the 1sec OFF time to advance the CD4017 to connect the next battery. The times for the 555 are not needing to be super accurate, within a minute or two. So far, though, The times have been inconsistent when using three 220uF Low ESR Caps in parallel. I looked at a 330uF Ceramic cap and almost ____ my pants, $22.

For the 10min Timer, I'd like to stay +/- 30sec, for the 20Min timer maybe +/- 1min, and for the 40min timer, +/- 2min. It really stinks to sit waiting 20/40min to see how close I am. And YES a uC would be great, but I want the project done long before I learn the language well enough to make this happen.

I have a few ICM7242IPA PDIP-8 Timers that would enable me to easily get accurate timing, but the chip does not seem to be able to alter the duty cycle so that I can increment the CD4017. DATASHEET

Help & Suggestions needed!
Thanks ALL!

Limiting factors are mostly leakage in large timing capacitors and high value resistors tend to "wander off" - I'd go for a 555 running at a more practical frequency and get longer periods by squirting the pulses through a CMOS ripple counter.

 

Limiting factors are mostly leakage in large timing capacitors and high value resistors tend to "wander off" - I'd go for a 555 running at a more practical frequency and get longer periods by squirting the pulses through a CMOS ripple counter.

As several people have suggested

 

Thanks Dana. I do realize that a UP was made for this project, and I may jump into that game shortly, but for now I will stick to the parts I have in hand. I may solicit your help on UP apparatus when I am ready though!

I will be happy to help.

Regards, Dana.

 

Hello,

You could do something like this.
See attached.

The CD4060 produces periods of 10, 20, 40 minutes. A CD4017B is used to select the time period via a momentary pushbutton. U2C, R4, C5 form a trailing edge detector to detect the end of the time period and it clocks a second CD4017B to select and activate each mosfet. When a new time is selected the timer is reset so it starts at the beginning of the time period. The circuit is designed for 12 volts (I missed the 5v supply) but a few RC values can easily be adjusted for 5v supply. The circuit requires five chips. I haven't breadboarded it but it works in simulation.

BTW
I didn't see your comment about a selector switch but the pushbutton circuit could be changed for a selector switch. Also, you show an LED hanging off of each mosfet gate. I don't know the type of LED but the CD4017B can only drive about 4ma reliably (MAX spec is 6ma). Might need to move each of those to the drain of each mosfet or drive them differently.

eT

View attachment 168245

 

eetech00,
Been admiring your take on the "Sequential Battery Float Charger." I appreciate you taking the time to come up with a solution. Surprisingly, I have all the chips(I believe): (2) CD4017, (1)CD4060, (1)Hex Inverter, and (1)AND Gate.
I like the solution for selecting the three different time periods, albeit requiring 2-3 additional chips.

The two 6.8uF Caps used for the initial timing (connected back-to-back), is this read as a 3.4uF/non-polarized cap?

My source voltage for the circuit will be two CR123 rechargeable batteries in series(6.0V) as I would expect them to last a fair amount of time(4 months continuous operation). I may be all wet with that guess, and if so I would resort to a spare cell phone charger@ 5V.

I had been pondering the Indicator LED's attached to the MOSFETs. Placing them on the drain will work just as well.
I would also have to add Indicator LED's for the three time periods. I should be able to tap off of the 4017 Selector IC, Q0, Q1, Q2, yes.

Building this iteration of the circuit is not set in stone, though, as I am in talks with eetech00 with respect to creating a uP for the job. Been wanting to get involved in this for some time. We'll see how our arrangement turns out.

 

eetech00,
Been admiring your take on the "Sequential Battery Float Charger." I appreciate you taking the time to come up with a solution. Surprisingly, I have all the chips(I believe): (2) CD4017, (1)CD4060, (1)Hex Inverter, and (1)AND Gate.
I like the solution for selecting the three different time periods, albeit requiring 2-3 additional chips.

The two 6.8uF Caps used for the initial timing (connected back-to-back), is this read as a 3.4uF/non-polarized cap?

Yes...The 4060 RC timing circuit requires a non-polar cap.

My source voltage for the circuit will be two CR123 rechargeable batteries in series(6.0V) as I would expect them to last a fair amount of time(4 months continuous operation). I may be all wet with that guess, and if so I would resort to a spare cell phone charger@ 5V.

I had been pondering the Indicator LED's attached to the MOSFETs. Placing them on the drain will work just as well.
I would also have to add Indicator LED's for the three time periods. I should be able to tap off of the 4017 Selector IC, Q0, Q1, Q2, yes.

You can tap off the 4017 but there's only about 4ma available from each output. You can add driver transistors if necessary, or use low power LEDs instead.

Building this iteration of the circuit is not set in stone, though, as I am in talks with eetech00 with respect to creating a uP for the job. Been wanting to get involved in this for some time. We'll see how our arrangement turns out.

umm....I think you meant dendak

Good luck,,

eT

 

Below is the LTspice simulation of a CD4040 12-bit counter (I don't have a model for the CD4060) driving a CD4017 .
With a 1.17s clock period, the Q9 (divide by 512) output has a 600s period (10 minutes).
You can see this sequentially advancing the CD4017 output every 10 minutes.

Note that you only require one timing chip as the Q10 output will have a 20 minute period and Q11 will have a 40 minute period.

 

Setup the first stage of the circuit by eetech00. Despite trying three different make of the 4017 decade counter (CD4017B, HCF4017B, & M74HC4017B) and could not get one to work. Tried multiple chips of each make, kept the diode, removed the diode, kept the cap, removed the cap, tried both 5V & 12V, moved the chip on the breadboard, Rewired...etc.

 

I see several problems:

Each LED need a resistor in series.

The clock has nothing to pull the signal to ground (it won't go there by itself). Add a 10kΩ resistor from the clock input to ground. A floating CMOS will float to an undefined state.
An open circuit CMOS input is not logic zero.
Never-ever let a CMOS input float.

If PB is a mechanical switch the contacts will bounce when energized, generating multiple clock pulses with each closing. You need to add a debounce circuit (Google it).

D1 serves no purpose and allows the Reset input to float to an undefined logic state. Remove it and connect output 3 directly to RESET.

 

You are trying to clock the clock with a mechanical push button. Thats
not good as they bounce due to inertia generating many clocks on a single
press.

You have to debounce the button. Many ways to do this, also using code in
UP.

Regards, Dana.

 

I see several problems:

Each LED need a resistor in series.

The clock has nothing to pull the signal to ground (it won't go there by itself). Add a 10kΩ resistor from the clock input to ground.
Never-ever let a CMOS input float.

If PB is a mechanical switch the contacts will bounce when energized, generating multiple clock pulses with each closing. You need to add a debounce circuit (Google it).



D1 serves no purpose and allows the Reset input to float to an undefined logic state. Remove it and connect output 3 directly to RESET.

Thanks crutschow & danadak!
The diode will likely be necessary later when I connect additional circuitry. I had tried it with and without. The LED's do need resistors, but given the 5V supply and testing, I omitted them as they would be momentary. The switch debounce circuitry was used initially and didn't "seem" to make a difference so I began leaving it out. But this would be the likely culprit.
Will add the debounce circuitry tomorrow AM and report back.

 

The LED's do need resistors, but given the 5V supply and testing, I omitted them as they would be momentary.

Being momentary is not important for survival of the LEDs or the IC, but even momentary excessive loading of the CMOS outputs could affect the operation of the IC.

 

So much for a "morning" reply.
Built the circuit below. Upon power-up, Pin 3(4017) lights up. Pressing the PB turns Pin 2 high, and with an additional press Pin 4 goes high. As one LED turns on, the other two LED's are off. However, this is consistent only when I press deliberately. If I press lightly or quickly the LED sequencing order can fail.

Note: R1 & R4 are 8.2k, not 8.2 Ohms


I have read that all inverters are not created equal for TTL circuits. These are the Inverters I have on hand:

- HCF4069UBEY(Hex Inverter)
- MC14584BCP(Hex Schmitt Trigger)
- MC74HC04(Hex Inverter High-Performance Silicon-Gate CMOS)
- CD4050BCN(Hex Non-Inverting Buffer)
- CD4010(Hex Buffers (Non-Inverting)


Further observations:
While waiting for replies, I did some more reading. I noticed that the 1uF capacitor I was using was polarized. I think it was a Tantalum cap. I switched it out for a .33uF ceramic cap and I could not replicate the bouncing effects. But!... I also tried the switch with no cap in the circuit and also had no fails. Then I reinserted the polarized cap and could not reproduce the fails either! Perplexed. Not sure if my values for resistors & cap are in the right ballpark, so insight on this would be helpful. From readings, I learned that the diode in the debouncing circuit helps speed up the switching. Also, the inverter should be taking care or the RC ramping characteristics.

Q: Any advantage to debouncing from low side rather than high side? I can't see any, other than what may be simpler for the system/circuit.

ALSO:
- MM74HC14N(Hex Inverting Schmitt Trigger) Now in circuit

Thanks peeps(people)...send me some more knowledge! Must have knowledge!

 

I have read that all inverters are not created equal for TTL circuits.

None of those circuits are TTL (bipolar), they are CMOS.

Use the Schmitt trigger for U2.